1. Field of the Invention
The present invention relates to a power supply device and an operation method of a power supply device, and in particular, to a power supply device, an operation method of a power supply device, an electronic apparatus, and an operation method of an electronic apparatus capable of efficiently reducing the power consumption of a plurality of power supplies with different voltages and of setting a starting sequence freely.
2. Description of the Related Art
In general, an imaging apparatus using a CMOS (complementary metal oxide semiconductor) sensor configured to include a photodiode and an MOS (metal oxide semiconductor) transistor is widespread.
The CMOS sensor includes a photodiode, a MOS transistor, and an amplifying circuit for amplifying a signal from a photodiode for every pixel and has many advantages that, for example, “XY addressing” or “packaging a sensor and a signal processing circuit in one chip” is possible. However, since the number of elements within one pixel is large, it has been difficult so far to reduce the chip size that determines the size of an optical system. In recent years, however, the CMOS sensor has been drawing attention as a technique of making a MOS transistor small is improved and a request of “packaging a sensor and a signal processing circuit in one chip” or “reducing the power consumption” is increased.
An operation principle of the CMOS sensor is that electric charges generated by photoelectrically converting light, which is received by a photodiode, are transferred through a transfer transistor in the unit of each pixel and are sequentially output at timing designated according to the pixel position. Moreover, an image is generated corresponding to the electric charges output in the unit of a pixel.
Here, when electric charges photoelectrically converted by the transfer transistor in the photodiode are transferred, the transfer of electric charges is controlled by a voltage applied to a gate of the transfer transistor. However, a potential pocket or a barrier is generated if the voltage applied to the gate is simply controlled in two values, and accordingly, the transfer becomes incomplete since the potential of the potential pocket is not flat and residual electric charges are generated. As a result, there has been a possibility that an afterimage or a random noise resulting from the back flow to the photodiode would be generated.
For this reason, there has been proposed a technique of suppressing an afterimage or a random noise by reducing residual electric charges by generating an intermediate electric potential for a predetermined period of time or more in order to make a control with a voltage having at least three values.
An example of the related art includes Japanese Patent No. 3667214.